0.5 Glossary  (Page 15/18)

Q

• Q fever highly infectious zoonotic disease caused by Coxiella burnetii that farmers can contract from their animals by inhalation
• quarantine the isolation of an individual for the purpose of preventing the spread of disease
• quaternary ammonium salts (quats) group of cationic detergents, named for the characteristic quaternary nitrogen atom that confers a positive charge, that make up an important class of disinfectants and antiseptics
• quaternary structure structure of protein complexes formed by the combination of several separate polypeptides or subunits
• quinolines class of antiprotozoan drugs long used for the treatment of malaria; interferes with heme detoxification
• quorum sensing cell-to-cell communication in bacteria; enables a coordinated response from cells when the population reaches a threshold density

R

• R plasmid plasmid containing genes encoding proteins that make a bacterial cell resistant to one or more antibiotics
• rabies contagious viral disease primarily transmitted by the bite of infected mammals that can cause acute encephalitis resulting in madness, aggressiveness, coma, and death
• radial immunodiffusion precipitin reaction in which antigen added to a well in an antiserum-impregnated gel diffuses, producing a precipitin ring whose diameter squared is directly proportional to antigen concentration
• rat-bite fever relapsing fever caused by either Bacillus moniliformis or Spirillum minor ; can be transmitted by the bite of a rat or through contact with rat feces or urine
• reaction center protein complex in a photosystem, containing a pigment molecule that can undergo oxidation upon excitation by a light-harvesting pigment, actually giving up an electron
• reactivation tuberculosis secondary infection by Mycobacterium tuberculosis that forms later in life; occurs when the bacteria escape from the Ghon complexes and establish focal infections at other sites in immunocompromised individuals
• reactive oxygen species (ROS) unstable and toxic ions and molecules derived from partial reduction of oxygen
• reading frame way nucleotides in mRNA are grouped into codons
• real-time PCR (quantitative PCR, qPCR) a variant of PCR involving the use of fluorescence to allow for the monitoring of the increase in double-stranded template during a PCR reaction as it occurs, allowing for the quantitation of the original target sequence
• receptor-mediated endocytosis a type of endocytosis in which extracellular ligands are targeted to specific cells through their binding to specific cell surface receptors
• recognition site a specific, often palindromic, DNA sequence recognized by a restriction enzyme that is typically four to six base pairs long and reads the same in the 5ʹ to 3ʹ direction on one strand as it does in the 5ʹ to 3ʹ direction on the complementary strand
• recombinant DNA molecule a DNA molecule resulting from the cutting and insertion of DNA from one organism into the DNA of another organism, resulting in a new combination of genetic material
• recombinant DNA pharmaceuticals pharmaceuticals produced as a result of genetic engineering
• recombinant DNA technology the process by which DNA from one organism is cut and new pieces of foreign DNA from a second organism are inserted, artificially creating new combinations of genetic material within the organism
• redox potential tendency for a molecule to acquire electrons and become reduced; electrons flow from molecules with lower redox potentials to those with higher redox potentials
• redox reaction pairing of an oxidation reaction with a reduction reaction
• reduction reaction chemical reaction that adds electrons to acceptor molecules, leaving them reduced
• reemerging infectious disease a disease that was once under control or largely eradicated that has begun causing new outbreaks due to changes in susceptible populations, the environment, or the pathogen itself
• reflection when light bounces back from a surface
• refraction bending of light waves, which occurs when a light wave passes from one medium to another
• refractive index a measure of the magnitude of slowing of light waves by a particular medium
• regulatory T cells class of T cells that are activated by self-antigens and serve to inhibit peripheral self-reacting T cells from causing damage and autoimmunity
• rejection process by which adaptive immune responses recognize transplanted tissue as non-self, mounting a response that destroys the tissue or leads to the death of the individual
• relapsing fever louse- or tickborne disease caused by Borrelia recurrentis or B. hermsii and characterized by a recurrent fever
• replica plating plating technique in which cells from colonies growing on a complete medium are inoculated onto various types of minimal media using a piece of sterile velvet, ensuring that the orientation of cells deposited on all plates is the same so that growth (or absence thereof) can be compared between plates
• replication bubble circular structure formed when the DNA strands are separated for replication
• replication fork Y-shaped structure that forms during the process of replication as DNA unwinds and opens up to separate the DNA strands
• replication process by which DNA is copied
• reporter genes genes that encode easily observable characteristics, allowing for their expression to be easily monitored
• repressible operon bacterial operon, that typically containing genes encoding enzymes required for a biosynthetic pathway and that is expressed when the product of the pathway continues to be required but is repressed when the product of the pathway accumulates, removing the need for continued expression
• repressor protein that suppresses transcription of a gene or operon in response to an external stimulus
• reservoir a living host or nonliving site in which a pathogenic organism can survive or multiply
• resident microbiota microorganisms that constantly live in the human body
• resolution the ability to distinguish between two points in an image
• restriction endonuclease (restriction enzyme) bacterial enzyme that cuts DNA fragments at a unique, often palindromic, recognition site; used in genetic engineering for splicing DNA fragments together into recombinant molecules
• restriction fragment length polymorphism (RFLP) a genetic variant identified by differing numbers or sizes of DNA fragments generated after digestion of a DNA sample with a restriction endonuclease; the variants are caused by the loss or gain of restriction sites, or the insertion or deleting of sequences between restriction sites.
• retort large industrial autoclave used for moist heat sterilization on a large scale
• retrospective study a research design that associates historical data with present cases
• retrovirus positive ssRNA virus that produces and uses reverse transcriptase to make an ssDNA copy of the retroviral genome that can then be made into dsDNA and integrate into the host cell chromosome to form a provirus within the host chromosome.
• reverse transcriptase enzyme found in retroviruses that can make a copy of ssDNA from ssRNA
• reverse transcriptase inhibitor classes of antiviral drugs that involve nucleoside analog competitive inhibition and non-nucleoside noncompetitive inhibition of the HIV reverse transcriptase
• reverse transcriptase PCR (RT-PCR) a variation of PCR used to obtain DNA copies of a specific mRNA molecule that begins with the conversion of mRNA molecules to cDNA by the enzyme reverse transcriptase
• Reye syndrome potentially life-threatening sequelae to some viral infections that result in the swelling of the liver and brain; aspirin use has also been linked to this syndrome
• Rh factor red blood cell surface antigen that can trigger type II hypersensitivity reactions
• rheostat a dimmer switch that controls the intensity of the illuminator on a light microscope
• rheumatic fever serious clinical sequela of an infection with Streptococcus pyogenes that can result in damage to joints or the valves of the heart
• rheumatoid arthritis systemic autoimmune disease in which immune complexes form and deposit in the joints and their linings, leading to inflammation and destruction
• rhinitis inflammation of the nasal cavity
• rhizines structures made of hyphae found on some lichens; aid in attachment to a surface
• ribonucleic acid (RNA) single-stranded nucleic acid composed of ribonucleotides; important in transcription and translation (protein synthesis)
• ribonucleotides RNA nucleotides containing ribose as the pentose sugar component and a nitrogenous base
• ribosome a complex intracellular structure that synthesizes proteins
• riboswitch small region of noncoding RNA found within the 5’ end of some prokaryotic mRNA molecules that may bind to a small intracellular molecule, influencing the completion of transcription and/or translation
• ribulose bisphosphate carboxylase (RuBisCO) first enzyme of the Calvin cycle responsible for adding a CO ₂ molecule onto a five-carbon ribulose bisphosphate (RuBP) molecule
• rifampin semisynthetic member of the rifamycin class that blocks bacterial RNA polymerase activity, inhibiting transcription
• rimantadine antiviral drug that targets the influenza virus by preventing viral escape from endosomes upon host cell uptake, preventing viral RNA release and subsequent viral replication
• ringworm a tinea (cutaneous mycosis of the skin), typically characterized by a round, red, slightly raised lesion that heals outward from the center, giving it the appearance of a round worm
• RNA interference (RNAi) process by which antisense RNAs or small interfering RNAs (siRNAs) interfere with gene expression by binding to mRNA, preventing translation and protein synthesis
• RNA polymerase enzyme that adds nucleotides to the 3’-OH group of the growing mRNA molecule that are complementary to the template strand, forming covalent phosphodiester bonds between the nucleotides in the RNA
• RNA splicing process of removing intron-encoded RNA sequences from eukaryotic primary transcripts and reconnecting those encoded by exons
• RNA transcript mRNA produced during transcription
• Rocky Mountain spotted fever potentially fatal tickborne disease caused by Rickettsia rickettsii characterized by fever, body aches, and a rash
• rogue form misfolded form of the PrP protein that is normally found in the cell membrane and has the tendency to aggregate in neurons, causing extensive cell death and brain damage
• rolling circle replication type of rapid unidirectional DNA synthesis of a circular DNA molecule
• roseola a rash-causing illness, most commonly affecting children, associated with human herpesvirus 6 (HHV-6)
• rough endoplasmic reticulum a type of endoplasmic reticulum containing bound 80S ribosomes for the synthesis of proteins destined for the plasma membrane
• route of administration method used to introduce a drug into the body
• rRNA type of stable RNA that is a major constituent of ribosomes, ensuring proper alignment of the mRNA and the ribosomes as well as catalyzing the formation of the peptide bonds between two aligned amino acids during protein synthesis
• rubella German measles, caused by the rubella virus
• runs (running) purposeful, directional movement of a prokaryotic cell propelled by counterclockwise flagellar rotation